The present invention relates to a photographic color temperature meter for measuring color temperature of a flash light used for phototaking.
Conventionally photographic film is arranged to reproduce proper colors when a photographing operation is carried out using a light source specified according to the film characteristic. For example, a film of type D reproduces proper colors when photographing in daylight whose color temperature is 5500 K., and a film of type A reproduces proper colors when photographing in a tungsten light whose color temperature is 3200 K. In other words, the color temperature of a light source for photographing should be kept as close as possible to that of the light source specified according to the film in use. Accordingly, in case the former temperature differs from the latter, it is necessary to correct colors by using a filter and the like, unless a photographer has a particular intention in phototaking.
In case the color temperature of the light source used for photographing is unstable, the photographer has to measure the color temperature and correct colors each time a photographing operation takes place. Therefore, the color temperature should be kept as constant as possible in a stable condition. In most photographing studios and the like, the color temperature is kept constant by means of periodical measurement of each light source. Further, the photographer often measures the color temperature of the light source for confirmation before starting photographing.
In conventional photographic color temperature meters capable of measuring flash light, in case of measuring flash light, it is unavoidable that stationary light such as ambient daylight is taken in together with the flash light. Hence, the light measurement result is Inevitably affected by the stationary light. Therefore, in the case of performing color temperature light measurement regarding only the flash light, it has been required to measure light after cutting off all light except for the light from a flash light source, by turning an ambience completely dark Just before the flash light measurement.
However, the light measurement of a flash light source was a most troublesome operation, because it reduces the operational efficiency of light measurement to turn the ambience completely dark every time photographing is performed. Further, in case of photographing at a place such as outside where stationary light can not be taken away easily, it was very difficult to measure the color temperature only of flash light. In the conventional photographic exposure meter, an aperture value for setting an exposure is obtained by means of a separate light measurement, i.e., by separating a flash light component and a stationary light component. However, the meter cannot output color temperature data solely based on the flash light with use of plural light receiving units whose one spectral sensitivity is different from another.